→ Temporary paralysis in Quarter Horses
- General weakness
- Periodic tremors and paralysis
- Respiratory problems (noise while breathing)
- Heavily muscled
- Varies in severity.
- May be life-threatening when heart or lungs are affected by paralysis.
- Homozygous horses show more severe symptoms than heterozygous individuals.
- Symptoms may occur more frequently after changes in diet, stress or transportation.
- Inproper signalling between brain and muscles/organs.
- Symptoms may be reduced with potassium-deficient diet (avoid Lucerne/Alfalfa in hay)
- Can be traced back to the sire “Impressive”.
Inheritance: autosomal dominant
→ Horses with one or two copies of the variant (HYPP/n or HYPP/HYPP) are affected.
|Genotype||The horse is:
|n/n||normal.||The horse has no copies of the genetic variant causitive for HYPP and therefore cannot pass it on to its offspring|
|HYPP/n||affected (heterozygous).||The horse is affected. The genetic variant will be passed on to its offspring with a probability of 50%. These foals will be affected.
|HYPP/HYPP||affected (homozygous).||The variant will be passed on to all of its offspring. All offspring will also be affected.
- Affected animals (HYPP/n or HYPP/HYPP) should not be used for breeding.
Testinformation: This test detects the change in the SCN4A gene.
Rudolph, J. A., Spier, S. J., Byrns, G., Rojas, C. V., Bernoco, D., & Hoffman, E. P. (1992). Periodic paralysis in quarter horses: a sodium channel mutation disseminated by selective breeding. Nature Genetics, 2(2), 144-147. doi: 10.1038/ng1092-144.
Further information is available at Online Mendelian Inheritance in Animals.